MELROSE — Rob Gronkowski interacted with about 500 youth athletes over the weekend at his two-day football camp at Melrose High School. Not one of them seemed too concerned with Gronkowski getting back on the field and returning to his All-Pro form for the Patriots.

Maybe it’s because they’re used to seeing Gronkowski rehabbing an injury this time of year. He rehabbed an ankle in 2012, his forearm and back in 2013, and now his right knee after a significant injury in December.

“I remember last year they all asked, ‘When are you going to be back?’ ” Gronkowski said Sunday morning. “I’m not lying, not one kid this time has asked am I going to be back? It just looks like they’re just having a lot of fun and that’s not even on their mind — which is cool, that I don’t have to answer to the kids.”

Gronkowski answers to the Patriots, and by all appearances he is progressing well from surgery in early January to repair a torn ACL and MCL. Though he hasn’t participated with his teammates in the offseason practices, he has been working with trainers on the field and in the weight room at Gillette Stadium.

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Gronkowski suffered the injury Dec. 8 when then-Browns safety T.J. Ward dived helmet-first directly into his knee, and Gronkowski waited a month for the swelling to go down before having Dr. James Andrews perform surgery. Gronkowski declined to put a timetable on his return and whether he can be available for the Patriots’ first game of the season, Sept. 7 at Miami.

“Just doing what I got to do, improving every week, and that’s all I can ask for,” Gronkowski said. “I just worry about what I’ve got to do, and what I’ve got to do right now is rehab and get better. Just take it week by week and day by day from here on out. We’ll see what happens and we’ll see where I’m at when it all starts.”

Gronkowski, 25, has sat out of the team portion of organized team activities because of injury for the last three seasons and is a strong candidate to start training camp on the physically unable to perform list. That would mean he cannot participate with his teammates but can work with trainers on the field. The Patriots can take him off the PUP list at any time during training camp, but if he remains on the list for the start of the regular season, by rule he must sit out the first six games.

The Patriots took Gronkowski off the PUP list before Week 1 last year, and carried him on the 53-man roster even though he was not ready to play. Gronkowski ultimately sat out for six games as he strengthened his forearm and back, and lasted seven games before suffering the knee injury.

Gronkowski is understandably frustrated to be rehabbing another injury this offseason — and one that could potentially affect his speed and NFL longevity — but he’s taking it in stride.

“Just got to go and work hard every day, and if you give it all you got when you’re at work, in the weight room and on the field, then you really can’t be disappointed,” he said.

Gronkowski, now almost five months after surgery, didn’t show any effects of a knee injury Sunday, and even did a little jump and chest bump with his brother, Gordie.

“That was like the weakest jump I’ve ever done — not even close to being dangerous,” Gronkowski said.

Gronkowski didn’t run around much, and spent his time at the camp taking photos and throwing passes to all the groups of kids.